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1801. BV photometry of NGC 2099 variables
ID:
ivo://CDS.VizieR/J/A+A/483/253
Title:
BV photometry of NGC 2099 variables
Short Name:
J/A+A/483/253
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rotation and solar-type magnetic activity are closely related to each other in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on star's rotation, and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the connection between rotation and activity. The open cluster NGC 2099 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters of different ages. We collected time series CCD photometric observations of this cluster in January 2004, and we determined the presence of periodicities in the flux variation related to the stellar rotation by Fourier analysis. We investigate the relations between activity manifestations, such as the light curve amplitude, and global stellar parameters. We have discovered 135 periodic variables, 122 of which are candidate cluster members. Determination of rotation periods of G- and K-type stars has allowed us to better explore the evolution of angular momentum at an age of about 500Myr. In our analysis, we have also identified 3 new detached eclipsing binary candidates among cluster members. A comparison with the older Hyades cluster (~625Myr) shows that the newly-determined distribution of rotation periods is consistent with the scenario of rotational braking of main-sequence spotted stars as they age. However, a comparison with the younger M34 cluster (~200Myr) shows that the G8-K5 members of these clusters have the same rotation period distribution. That is, G8-K5 members in NGC 2099 seem to have experienced no significant braking in the age range from ~200 to ~500Myr. Finally, NGC 2099 members have a smaller level of photospheric magnetic activity, as measured by light curve amplitude, than in younger stars of the same mass and rotation, suggesting that the activity level also depends on some other age-dependent parameters.
1802. BV photometry of 6 SMC stellar clusters
ID:
ivo://CDS.VizieR/J/A+A/561/A106
Title:
BV photometry of 6 SMC stellar clusters
Short Name:
J/A+A/561/A106
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar clusters in the Small Magellanic Cloud (SMC) are useful probes to study the chemical and dynamical evolution of this neighbouring dwarf galaxy, enabling inspection of a large period covering over 10Gyr. The main goals of this work are the derivation of age, metallicity, distance modulus, reddening, core radius and central density profile for six sample clusters, in order to place them in the context of the Small Cloud evolution. The studied clusters are: AM 3, HW 1, HW 34, HW 40, Lindsay 2, and Lindsay 3, where HW 1, HW 34, and Lindsay 2 are studied for the first time. Optical Colour-Magnitude Diagrams (V, B-V CMDs) and radial density profiles were built from images obtained with the 4.1m SOAR telescope, reaching V~23. The determination of structural parameters were carried out applying King profile fitting. The other parameters were derived in a self-consistent way by means of isochrone fitting, which uses the likelihood statistics to identify the synthetic CMDs that best reproduce the observed ones. Membership probabilities were determined comparing the cluster and control field CMDs. Completeness and photometric uncertainties were obtained performing artificial star tests. The results confirm that these clusters (except HW 34, identified as a field fluctuation) are intermediate-age clusters, with ages between 1.2Gyr (Lindsay 3) and ~5.0Gyr (HW 1). In particular HW 1, Lindsay 2, and Lindsay 3 are located in a region that we called West Halo, where studies on ages and metallicity gradients are still lacking. Moreover Lindsay 2 was identified as a moderately metal-poor cluster with [Fe/H]=-1.4+/-0.2dex, lower than expected from the age-metallicity relation by Pagel & Tautvaisiene (1998MNRAS.299..535P). We also found distances varying from ~53 to 66kpc, compatible with the large depth of the SMC.
1803. BV photometry of stars in NGC 6866
ID:
ivo://CDS.VizieR/J/AcA/59/193
Title:
BV photometry of stars in NGC 6866
Short Name:
J/AcA/59/193
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of 19 variable stars and two blue stragglers in the field of the open cluster NGC 6866. Three of the variable stars we classify as delta Sct, two as g Dor, four as WUMa, two as ellipsoidal variables, and one as an eclipsing binary. Seven stars show irregular variability. Two of the pulsators, delta Sct star NGC 6866-29 and gamma Dor star NGC 6866-21, are multiperiodic.
1804. BV photometry of stars in the LMC
ID:
ivo://CDS.VizieR/J/AJ/131/407
Title:
BV photometry of stars in the LMC
Short Name:
J/AJ/131/407
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed a field in the disk of the LMC on two consecutive nights in search of rapid variable stars. We found two pulsating stars of type RRab and Scuti and four binary stars; among the latter we found one sdB or cataclysmic variable below the LMC blue main sequence and three very close binary systems on the main sequence.
1805. BV photometry of Trumpler 14 and 16
ID:
ivo://CDS.VizieR/J/ApJ/549/578
Title:
BV photometry of Trumpler 14 and 16
Short Name:
J/ApJ/549/578
Date:
21 Oct 2021
Publisher:
CDS
Description:
H-R diagrams are presented for the very young galactic clusters Trumpler 14 and Trumpler 16, which are the two most populous clusters in the region of vigorous star formation surrounding {eta} Carinae. Point spread function photometry of UBV CCD images is presented down to V~19 for over 560 stars in Tr 16 and 290 stars in Tr 14. We have also obtained similar data for a local background field. After determining cluster membership through proper motions from a previous work, we find that the reddening of cluster members is significantly lower than that of the local background stars. Thus, we are able to use individual reddenings to identify likely members at far deeper levels than possible with proper motions. This work has revealed a significant population of pre-main-sequence (PMS) stars in both clusters. The location of the PMS stars in the H-R diagram indicates that the theoretical "stellar birthline" of Palla & Stahler (1990ApJ...360L..47P, follows the locus of stars far better than that of Beech & Mitalas (1994ApJS...95..517B). Comparison with both pre- and post-main-sequence isochrones also reveals that although intermediate-mass stars have been forming continuously over the last 10Myr, the high-mass stars formed within the last 3Myr. There is no evidence that the formation of the intermediate-mass stars was truncated by the formation of the high-mass stars.
1806. BV photometry of variable stars in SMC
ID:
ivo://CDS.VizieR/J/AJ/123/3216
Title:
BV photometry of variable stars in SMC
Short Name:
J/AJ/123/3216
Date:
21 Oct 2021
Publisher:
CDS
Description:
B and V photometry has been obtained for variable stars in the northeast arm of the Small Magellanic Cloud (SMC). Periods and light curves have been determined for 237 periodic variables, including 201 Cepheids, 68 of which are newly discovered. Fundamental-mode Cepheids and first-overtone mode Cepheids are generally well separated in the BV color-magnitude diagram, with the latter having bluer mean colors than the former. The Cepheid period-color relationship for this outlying SMC field is indistinguishable from that seen in more centrally located SMC fields and is bluer than theoretical predictions. The red edge to the populated portion of the instability strip shifts to bluer colors for fainter Cepheids. There is support from our sample for a previously reported steepening in the slope of the period-luminosity relation for fundamental-mode Cepheids near a period of 2 days. The Cepheids of the northeast arm may be closer to us than are those of the main body of the SMC, but the difference is smaller than or equal to about 4kpc, comparable to the tidal radius of the SMC.
1807. BV photometry of V532 Mon
ID:
ivo://CDS.VizieR/J/AJ/152/120
Title:
BV photometry of V532 Mon
Short Name:
J/AJ/152/120
Date:
21 Oct 2021
Publisher:
CDS
Description:
The first two sets of complete charge-coupled device light curves in the B and V bands of the short-period binary system, V532 Mon, are presented. The light curves are analyzed with spot models using the Wilson-Devinney code. V532 Mon is found to be an A-subtype intermediate-contact binary with a degree of contact factor of f=47.1%(+/-2.7%), a mass ratio of q=0.2502(+/-0.0019), and a cool spot on the primary component. The period changes of the system are investigated by combining newly determined times of light minimum with others published in the literature. We found that the general trend of the observed-calculated (O-C) curve shows a downward parabolic variation that corresponds to a long-term decrease in the orbital period at a rate of dP/dt=-1.716(+/-0.002)*10^-7^dyr^-1^. The long-term decrease of the orbital period can be explained by mass transfer from the more-massive component to the less massive one. The long-time period decrease, the intermediate-contact configuration, and the astrophysical parameters of the binary system suggest that V532 Mon will evolve into high fill-out, extreme mass-ratio overcontact binaries.
1808. BVRcIc photometry of NGC 821 globular clusters
ID:
ivo://CDS.VizieR/J/MNRAS/385/361
Title:
BVRcIc photometry of NGC 821 globular clusters
Short Name:
J/MNRAS/385/361
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a photometric study of globular clusters around the isolated elliptical galaxy NGC 821. B, V and R-band photometry come from the Mini-Mosaic imager on the 3.5-m Wisconsin Indiana Yale NOAO (WIYN) telescope. Observations were conducted between November 30 - December 2, 2005. Average seeing conditions were ~0.7". Two Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 (WFPC2) fields were analysed in the V and I-bands. Objects in this catalogue are the globular cluster candidates according to the selection criteria detailed in the journal article. Astrometric solution is from USNO-B stars. Note the center of NGC 821 on this system is located at 02:08:21.118 +10:59:42.21. Photometry has been corrected for Galactic extinction and we used a distance modulus of m-M=31.75 in our analysis.
1809. BVRc light curves of 5 CoRoT RR Lyrae stars
ID:
ivo://CDS.VizieR/J/A+A/570/A100
Title:
BVRc light curves of 5 CoRoT RR Lyrae stars
Short Name:
J/A+A/570/A100
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-precision, space-based photometric missions like CoRoT and Kepler have revealed new and surprising phenomena in classical variable stars. Such discoveries were the period doubling in RR Lyrae stars and the frequent occurrence of additional periodicities some of which can be explained by radial overtone modes, but others are discordant with the radial eigenfrequency spectrum. We search for signs of period doubling in CoRoT RR Lyrae stars. The occurrence of this dynamical effect in modulated RR Lyrae stars might help us to gain more information about the mysterious Blazhko effect. The temporal variability of the additional frequencies in representatives of all subtypes of RR Lyrae stars is also investigated.
1810. BVRH{alpha} photometry of candidates Be stars
ID:
ivo://CDS.VizieR/J/ApJ/652/458
Title:
BVRH{alpha} photometry of candidates Be stars
Short Name:
J/ApJ/652/458
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present B, V, R, and H{alpha} photometry of eight clusters in the Small Magellanic Cloud, five in the Large Magellanic Cloud, and three Galactic clusters and use two-color diagrams (2-CDs) to identify candidate Be star populations in these clusters. We find evidence that the Be phenomenon is enhanced in low-metallicity environments, based on the observed fractional early-type candidate Be star content of clusters of age 10-25Myr.

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